In arc welding, such as for example an orbital welder, a welder power supply is used that produces a low voltage high current power source to maintain a stable arc. The arc is initiated or struck by a high voltage breakdown across the gap between the electrode and the workpiece. Once the arc is struck, the voltage across the gap is much lower than the breakdown voltage and the current increases substantially. An arc start circuit may be used to strike the arc, and then the welder power supply is used during the welding operation.
One type of welder that is commonly used today is an orbital welder, in which an electrode revolves around the weld site during a welding operation. The electrode movement occurs within a weld head that generally surrounds and generally encloses the weld site. An orbital welder, for example, is commonly used for butt welding two tubes or pipes together. During some types of welding such as for example TIG welding used for stainless steel tubing, it is important to provide an inert purge gas at the weld site. The purge gas prevents oxidation and other deleterious effects during the welding operation The purge gas is provided within the tubing (ID purge) and around the outside of the tubing (OD purge).